Field of the Invention
The present invention relates to a variable valve lift system and, more particularly, to a variable valve lift system capable of implementing four or more valve lifts.
Description of Related Art
An internal combustion engine receives fuel and air into a combustion chamber and burns the same to generate power. When taking in air, an intake valve is operated by driving of a camshaft, and while the intake valve is open, air is taken in to the combustion chamber. Also, an exhaust valve is operated by driving of the camshaft, and while the exhaust valve is open, air is discharged from the combustion chamber.
Here, however, optimal intake valve and exhaust valve operations are varied depending on a rotation speed of an engine. That is, an appropriate lift or valve opening/closing time is varied depending on a rotation speed of the engine. In order to implement appropriate valve operations according to rotation speeds of an engine, a variable valve lift (VVL) apparatus including a plurality of cams designed to have various shapes and driving a valve to be operated at different lifts according to RPMs of an engine has been studied.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.